Răspuns :
520-[680:a+4x50]=286
680:a+200=520-286
680:a+200=234
680:a=34
a=680:34
a=20
680:a+200=520-286
680:a+200=234
680:a=34
a=680:34
a=20
520-[680:a+4*(20+12+18)]=286 680:a+4*50=234 680:a+200=234 680:a=34 a= 20 Coronita?